INDIA - Highly putrefied poultry litter being used as feed in fish tanks in Andhra Pradesh is generating a toxic biocycle.

The litter, when added to fish tanks, contaminates the water and increases the fluctuation of biological oxygen demand (BOD), reports TheHindu.

It also accentuates the ectoparasite problem, leading to ulcers in fish. To control the parasite, fish farmers use highly toxic pesticides which penetrate into the biocycle posing a serious health hazard to the end consumer.

About 1,200 poultry farmers in the state grow birds in cages allowing their litter (excreta) to accumulate at the bottom of the cages. Due to poor practice this is only removed once a year.

Around 90 per cent of this is used in fish farms as feed. The rest is used as manure.

“The problem has been there for the last few decades but the authorities concerned have been soft-pedalling the issue. Not that the poultry farmers or fish-rearers are unaware of the serious harm involved, but both have found easy solutions — the former’s concern is to dispose it the easy way and the latter sees it as a low-cost way of increasing the phytoplankton in their tanks,” explains city-based agricultural scientist R. Suresh Kumar.

Poultry litter, when accumulated for a long period, releases polluted gases with bad odour causing pollution in air and ground water besides turning the place a breeding ground for housefly maggots which survive on litter and release greenhouse gases (GHG) — ammonia, methane, carbon dioxide, nitrous oxide and hydrogen sulphide — in the environment.

“Most of these pesticides are based on the organic phosphorous group and synthetic pyrethroids, which cause neuro-toxic effect on fish consumers and also these pesticides are carcinogenic,” says Mr Kumar.

A fresh challenge is that the fish ectoparasites have developed resistance to the existing pesticides and farmers are going for new toxic chemicals. To control housefly maggots, farmers use highly toxic pesticides which contaminate poultry litter used as fish feed.

Suggesting methods to utilise the manure, Mr. Suresh Kumar says biomethanation, incineration and composting could help overcome the problem in addition to generating power.